Abstract
Inconel 625 is a Nickel alloy which was used in fabrication of high temperature resistance and corrosion resistance components, such as metal bellows used in expansion joints in aircraft, aerospace and petroleum industry. The paper focuses on studying the effect of continuous current and pulsed current in welding Inconel 625 sheets using Micro Plasma Arc Welding (MPAW) process. Welding was carried out on 0.25 mm thick Inconel 625 sheets using continuous current mode and pulsed current mode separately keeping all other welding parameters constant. Weld quality characteristics like bead profile, micro structure, hardness and tensile properties are investigated and it is found that the usage of pulsed current leads to better weld quality characteristics when compared to continuous current mode
Highlights
Inconel 625 is extremely versatile austenitic nickel based super alloys with excellent strength and good ductility at high temperature
Grain size of continuous current and pulsed current is measured by using Scanning Electron Microscope (SEM) (Make: INCA Penta FETx3, Model:7573)
It is understood that pulsed current specimen failed at Heat Affected Zone (HAZ), where as continuous current specimen failed at Fusion zone
Summary
Inconel 625 is extremely versatile austenitic nickel based super alloys with excellent strength and good ductility at high temperature. Inconel 625 can be joined using variety of welding methods, including Gas Tungsten Arc Welding, Plasma Arc Welding, Laser Beam Welding and Electron Beam Welding Of these methods, low current PAW (Micro PAW) has attracted particular attention and has been used extensively for the fabrication of metal bellows, diaphragms which require high strength and toughness. The main objective of the present work is to study the weld quality characteristics of continuous current and pulsed current MPAW process. There are many influential process parameters which effect the weld quality characteristics of pulsed current MPAW process like peak current, back current, pulse rate, pulse width, flow rate of shielding gas, flow rate of purging gas, flow rate of plasma gas, welding speed etc. From the earlier works [3,4,5,6] carried out on pulsed current MPAW it was understood that the peak current, base current, pulse rate and pulse width are the dominating parameters which effect the weld quality characteristics.
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